The invention relates to the burying of electrical or other cable, in a manner which assures protection against attack by gnawing or burrowing rodents.
Underground cable-laying is a well-established art that is currently implemented by tractor vehicles or tractor-drawn vehicles which drag an earth plow at desired cable-burial depth and which continuously guide cable to burial depth, via the trailing end of the plow. With such equipment, it is merely the cable itself which is buried, the same having been manufactured at a factory to the capacity of a suitable drum, via which it is stored, shipped, and mounted to the cable-laying equipment, the prefabricated cable being paid out in the course of cable-laying vehicle travel. In this situation, any rodent protection for the cable must necessarily be a part of the premanufactured cable, i.e., as paid out in the course of cable-laying, but such fabrication for protection against rodents necessarily involves added bulk, materials, transportation, handling and inventory cost.
U.S. Pat. No. 3,604,215 discloses apparatus and a technique of burying cable wherein a conductive mud, which may include Portland cement, is mixed on a plowing vehicle that is said to excavate a subsurface passage into which fresh mix is injected by a "mud jack" directly into the passage adjacent the pay-out exit of cable from the plow share, the mud or mortar discharge being under such hydraulic pressure as to force intimate contact with all metal surfaces and with confines of the excavated passage, squeezing out water and air from the soil, and compacting undisturbed soil, to thereby form an electrical grounding medium, presumably in aid of the function of the electrical grounding cable or wire implanted therewith.
The art cited in said patent is substantial and represents a century of effort directed to the burial of cable, including the use of cement in that connection. Therefore, reference is made to said cited patents for additional background information.
In spite of the indicated background of patent literature, I am unaware of any prior method or apparatus which addresses the problem of economics, i.e., inexpensive, efficient use of materials to bury a communications cable, such as a non-conductive cable containing plural optical-fiber channels so as to provide inherent continuous protection of the cable against rodent attack.